package embed

import (
	"net"
	"net/url"

	"go.etcd.io/etcd/server/v3/embed"
)

const (
	DefaultHost = "localhost"
	DefaultPort = "0"
)

// Config struct provides the configuration options for an etcd instance.
type Config struct {
	Name      string
	PeerURL   *url.URL
	ClientURL *url.URL
	LogLevel  string
	embed     *embed.Config
}

// assignedAddress provides functionality to find an open host:port combination
type assignedAddress struct {
	host, port string
}

// assign tries to claim a URL using the provided host and port. A connection
// will be established to the assigned address to prevent other processes from
// attempting to claim the host:port for 60s.
//
// If no host is provided, then localhost will be used as a default.
//
// If no port is provided, then an available port will be selected at random.
func (a *assignedAddress) assign(url *url.URL) error {
	l, err := reserve(url.Hostname(), url.Port())
	if err != nil {
		return err
	}
	defer l.Close()
	a.host, a.port, err = net.SplitHostPort(l.Addr().String())
	return err
}

// reserve will reserve the host:port combination. If no host is provided, then
// localhost is used. If no port is provided, then one is selected at random
// from the pool of available ports.
func reserve(host, port string) (net.Listener, error) {
	if host == "" {
		host = DefaultHost
	}
	if port == "" {
		port = DefaultPort
	}

	addr, err := net.ResolveTCPAddr("tcp", net.JoinHostPort(host, port))
	if err != nil {
		return nil, err
	}
	return net.ListenTCP("tcp", addr)
}

// url returns the assignedAddress as a url.URL object
func (a *assignedAddress) url() url.URL {
	return url.URL{
		Scheme: "http",
		Host:   net.JoinHostPort(a.host, a.port),
	}
}